1. Field of the Invention
The present invention relates to an image forming method and apparatus capable of effectively positioning a cleaning unit. More specifically, the present invention relates to an image forming apparatus including a cleaning unit detachably provided thereto and effectively positioned based on a positioning reference, a cleaning unit provided to the image forming apparatus, and a method of positioning the cleaning unit.
2. Discussion of the Related Art
JP 05-323704 discloses an image forming apparatus with an intermediate transferring system includes, for example, a photoconductive drum serving as an image bearing member and bearing a toner image on the photoconductive drum according to a corresponding electrostatic latent image, an intermediate transfer member serving as an intermediate transfer member and receiving the toner image formed on a surface of the photoconductive drum, a primary transfer member transferring the toner image from the photoconductive drum onto the intermediate transfer belt, and a secondary transferring member transferring the toner image from the intermediate transfer belt onto a recording medium. When the background image forming apparatus includes a tandem-type system, a plurality of photoconductive drums are provided to form respective toner images.
The intermediate transfer belt includes a plurality of layers. The plurality of layers includes a base layer produced by a partially elastic material, for example, a fluorocarbon resin, a polyvinylidene sheet, a polyimide resin, and the like, and a surface layer or a coated layer produced by a resin having a smoothing ability, for example, a fluorocarbon resin.
In the background image forming apparatus, the toner images formed on the respective surfaces of the plurality of photoconductive drums are transferred onto the intermediate transfer belt to form an overlaid toner image as a primary transfer, and then the overlaid toner image is transferred onto the recording medium as a secondary transfer. After the secondary transfer is performed, toner remaining on the intermediate transfer belt is removed by a cleaning unit. The cleaning unit employs a method of removing residual toner, for example, by scraping the toner physically with a cleaning blade and/or by removing residual toner statically with a brush roller.
Recently, there is a strong demand that image forming apparatuses using an electrostatic copying method have better image forming productivity. To respond the above-described demand, toner that reacts well to the the electrostatic latent image has been studied. This new toner has greater sphericity and smaller particle diameter so as to form higher definition images. However, the smaller particle diameter makes it more difficult to remove residual toner from an intermediate transfer belt. Therefore, the new toner requires that the cleaning unit be replaced within a predetermined period of maintenance appropriate for the new toner. When the life of the cleaning unit is shorter than the other units in the image forming apparatus, it is more preferable that the cleaning unit is replaced separately from the other units.
In the previously described conventional tandem image forming apparatus (i.e., multi-color), the image forming apparatus includes a plurality of photoconductive drums corresponding to respective colors such as black, yellow, magenta, cyan, and the like. Because of the presence of the plurality of photoconductive drums, space for other units becomes limited. To accommodate this reduced space, the cleaning member is disposed opposite to a tension roller supporting the intermediate transfer belt with tension. The position of the tension roller, however, varies according to a circumferential length of the intermediate transfer belt. Thus, it is difficult to mount the cleaning member in an easily detachable manner to the image forming apparatus. Furthermore, it is more difficult to position the cleaning member according to the tension roller in an axial direction of the tension roller.
To solve the above-described problem regarding the positioning of the cleaning member, and to allow easier installation and removal, JP 2001-075374 has proposed a technique whereby a tension roller supporting an intermediate transfer belt is held by a holding member via a rotative shaft of the tension roller to be movable in one direction. By positioning the cleaning unit by the holding member, the cleaning member can effectively contact the intermediate transfer belt.
JP 2004-070305 has proposed another technique whereby a process cartridge including at least a plurality of electrostatic image bearing members and an intermediate transfer member is detachably disposed in an image forming apparatus. The plurality of electrostatic image bearing members and a supporting shaft of the intermediate transfer member are preliminarily positioned to the process cartridge. When the process cartridge is mounted on a predetermined position, the plurality of electrostatic image bearing members and the supporting shaft of the intermediate transfer member are properly positioned by a first positioning member mounted on the image forming apparatus. Thus, the plurality of electrostatic image bearing members and the supporting shaft of the intermediate transfer member are positioned in high precision with a simple structure.
However, the previously identified conventional approaches are deficient because they are prone to errors in positioning the cleaning unit. Thus, what is desired, as discovered by the present inventors is an image forming method and apparatus capable of effectively positioning a cleaning unit.